澳大利亚的灌区管理及其启示

澳大利亚灌区管理一般采取用水户参与的公司运作模式,通过灌溉公司和用水户所拥有的水权进行灌区水资源的分配,水权可以进入水市场进行临时或者永久的交易。灌区通过现代信息化技术来实现灌区水资源利用效率的提高和农户经济收入的提高,并通过专门机构来负责环境用水水权。结合我国灌区实际,提出可供我国灌区管理借鉴的经验。     

Quality of Building Construction Materials (Cement) in Developing Countries

The aim of the project reported in this paper is to determine the quality of cement used in building construction operations in a typical developing country, Bangladesh. Comparison is made to the strength required in the standard ASTM specifications. Cement is the basic binding material in concrete, and the quality of concrete is dependent upon the quality of the cement used. In developing countries such as Bangladesh, the quality of construction materials, including cement, may not conform to international standards because of poor quality control, governmental corruption, and problems associated with transportation and storage. Investigations involving cement mortar show that 26.67% of test results satisfied standard compressive strength for 3 days, 6.67% of test results satisfied standard compressive strength for 7 days, and no test results satisfied standard compressive strength for 28 days. The aforementioned data indicate that there is a distinct problem with the quality of cement in a typical developing country such as Bangladesh. The results of this study may alert contractors and engineers to concerns about the quality of cement and assist local governments to take the necessary action to control the quality of this important construction material.     

A hybrid defocused region segmentation approach using image matting

Multidimensional Systems and Signal Processing - In this paper, a hybrid defocused region segmentation using image matting is proposed. The technique incorporates three sharpness metrics which are...     

Influence of pentanol and dimethyl ether blending with diesel on the combustion performance and emission characteristics in a compression ignition engine under low temperature combustion mode

Dimethyl ether (DME) and n-pentanol can be derived from non-food based biomass feedstock without unsettling food supplies and thus attract increasing attention as promising alternative fuels, yet some of their unique fuel properties different from diesel may significantly affect engine operation and thus limit their direct usage in diesel engines. In this study, the influence of n-pentanol, DME and diesel blends on the combustion performance and emission characteristics of a diesel engine under low-temperature combustion (LTC) mode was evaluated at various engine loads (0.2–0.8 MPa BMEP) and two Exhaust Gas Recirculation (EGR) levels (15% and 30%). Three test blends were prepared by adding different proportions of DME and n-pentanol in baseline diesel and termed as D85DM15, D65P35, and D60DM20P20 respectively. The results showed that particulate matter (PM) mass and size-resolved PM number concentration were lower for D85DM15 and D65P35 and the least for D60DM20P20 compared with neat diesel. D60DM20P20 turned out to generate the lowest NO_x emissions among the test blends at high engine load, and it further reduced by approximately 56% and 32% at low and medium loads respectively. It was found that the combination of medium EGR (15%) level and D60DM20P20 blend could generate the lowest NO_x and PM emissions among the tested oxygenated blends with a slight decrease in engine performance. THC and CO emissions were higher for oxygenated blends than baseline diesel and the addition of EGR further exacerbated these gaseous emissions. This study demonstrated a great potential of n-pentanol, DME and diesel (D60DM20P20) blend in compression ignition engines with optimum combustion and emission characteristics under low temperature combustion mode, yet long term durability and commercial viability have not been considered.     

Optimal control overhead based multi-metric routing for MANET

Wireless Networks - During the last two decades, there has been a tremendous growth in the use of MANETs, not only due to the development of the technology but also due to their high flexibility....     

A novel framework for G/M/1 queuing system based on scheduling-cum-polling mechanism to analyze multiple classes of self-similar and LRD traffic

Provisioning guaranteed Quality of Service (QoS) in multiservice wireless internet is challenging due to diverse nature of end-user traffic (e.g., voice, streaming video, interactive gaming) passing through heterogeneous interconnected domains with their own policies and procedures. Numerous studies have shown that multimedia traffic carried in wireless internet possesses self-similar and long-range dependent characteristics. Nonetheless, published work on wireless traffic modeling is merely based on traditional Poisson traffic distribution which fails to capture these characteristics and hence yield misleading results. Moreover, existing work related to self-similar traffic modeling is primarily based on conventional queuing and scheduling combinations which are simple approximations.This paper presents a novel analytical framework for G/M/1 queuing system based on realistic internet traffic distribution to provide guaranteed QoS. We analyze the behavior of multiple classes of self-similar traffic based on newly proposed scheduling-cum-polling mechanism (i.e., combination of priority scheduling and limited service polling model). We formulate the Markov chain for G/M/1 queuing system and present closed form expressions for different QoS parameters i.e., packet delay, packet loss rate, bandwidth, jitter and queue length. We develop a customized discrete event simulator to validate the performance of the proposed analytical framework. The proposed framework can help in building comprehensive service level agreements for heterogeneous wireless domains.